Patent Application
20240328943
Aspects of this technology are described in “Naphthalene-based silica nanoparticles as a highly sensitive fluorescent chemosensor for mercury detection in real seawater,” Journal of Molecular Liquids, Volume 374, 121294, which is incorporated herein by reference in its entirety.
The present disclosure is directed to a sensor, particularly a sensor functionalized by naphthalene-based silica nanoparticles for detecting mercury ions.
The “background” description provided herein is to present the context of the disclosure generally. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.
Apart from daily life benefits, the contemporary and rapid developments in agricultural industries have harmed the global community by contaminating natural resources with hazardous and harmful chemicals [E. Gaggelli, H. Kozlowski, D. Valensin, G. Valensin, Copper Homeostasis and Neurodegenerative Disorders (Alzheimer's, Prion, and Parkinson's Diseases and Amyotrophic Lateral Sclerosis), Chem. Rev. 106 (2006) 1995-2044; D. T. Quang, J. S. Kim, Fluoro- and Chromogenic Chemodosimeters for Heavy Metal Ion Detection in Solution and Biospecimens, Chem. Rev. 110 (2010) 6280-6301; and M. Mansha, S. Akram Khan, M. A. Aziz, A. Zeeshan Khan, S. Ali, M. Khan, Optical Chemical Sensing of Iodide Ions: A Comprehensive Review for the Synthetic Strategies of Iodide Sensing Probes, Challenges, and Future Aspects, Chem. Rec. 22 (2022)]. The major water-borne pollutants such as pesticides, fertilizers, pharmaceuticals, volatile organic compounds, and heavy metal ions (Hg2+, Cd2+, Zn2+, Pb2+, etc.) have created an alarming situation for human health and living organisms. Among these pollutants, heavy metals possess detrimental effects on human organic tissues through air inhalation, food chain, and water circulation [G. Aragay, J. Pons, A. Merkogi, Recent Trends in Macro-, Micro-, and Nanomaterial-Based Tools and Strategies for Heavy-Metal Detection, Chem. Rev. 111 (2011) 3433-3458]. Mercury is the most prominent pollutant found in oceans, seas, rivers, and lakes. Specialists have estimated the amount of mercury in the seas is about 4000-10,000 tons annually, where 40% of that comes from natural sources and the other 60% from anthropogenic activities [M. F. Flores-Arce, Proceedings of the International Symposium on Selenium-Mercury Interactions, Biol. Trace Elem. Res. 119 (2007) 193-194].
Mercury exists in different oxidation states (Hg2+, Hg+, Hg0, [CH3Hg]+) and is considered the leading cause of contamination in drinking water. These different forms of Hg are discharged into the environment through medical, industrial waste, and gold mining activities, thereby increasing the levels of mercury in nature [T. W. Clarkson, L. Magos, The toxicology of mercury and its chemical compounds, Crit. Rev. Toxicol. 36 (2006) 609-662; and J. F. Risher, R. A. Nickle, S. N. Amler, Elemental mercury poisoning in occupational and residential settings, Int. J. Hyg. Environ. Health. 206 (2003) 371-379]. Mercuric mercury (Hg2+) is the most stable form of mercury existing in nature [R. M. Gardner, J. F. Nyland, E. K. Silbergeld, Differential immunotoxic effects of inorganic and organic mercury species in vitro, Toxicol. Lett. 198 (2010) 182-190].
Even a small quantity of mercury that enters the human body can cause irreversible harm to vital organs and tissues, including the kidneys, liver, brain, and nervous/immune system, leading to the development of mobility and cognitive disorders [G. Aragay, J. Pons, A. Merkogi, Recent Trends in Macro-, Micro-, and Nanomaterial-Based Tools and Strategies for Heavy-Metal Detection, Chem. Rev. 111 (2011) 3433-3458]. According to the Environmental Protection Agency (EPA), the national primary drinking water regulations (NPDWR) enforce 2 ppb of Hg2+ as the maximum concentration permissible in drinking water.
Analytical techniques such as inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectroscopy (AAS), plasma-atomic emission spectroscopy (AES), voltammetry, electrochemiluminescence (ECL), gas chromatography (GC), high-performance liquid chromatography (HPLC), titration and electrochemical process have been employed to monitor Hg2+ ions concentrations [R. Tel-Vered, J. S. Kahn, I. Willner, Layered Metal Nanoparticle Structures on Electrodes for Sensing, Switchable Controlled Uptake/Release, and Photo-electrochemical Applications, Small. 12 (2016) 51-75; V. Schroeder, S. Savagatrup, M. He, S. Lin, T. M. Swager, Carbon Nanotube Chemical Sensors, Chem. Rev. 119 (2019) 599-663; B.-P. Qi, L. Bao, Z.-L. Zhang, D.-W. Pang, Electrochemical Methods to Study Photoluminescent Carbon Nanodots: Preparation, Photoluminescence Mechanism and Sensing, ACS Appl. Mater. Interfaces. 8 (2016) 28372-28382; N. Wongkaew, M. Simsek, C. Griesche, A. J. Baeumner, Functional Nanomaterials and Nanostructures Enhancing Electrochemical Biosensors and Lab-on-a-Chip Performances: Recent Progress, Applications, and Future Perspective, Chem. Rev. 119 (2019) 120-194; and S. Ali, M. Mansha, N. Baig, S. A. Khan, Recent Trends and Future Perspectives of Emergent Analytical Techniques for Mercury Sensing in Aquatic Environments, Chem. Rec. 22 (2022) e202100327]. The conventional techniques for Hg2+ detection have certain limitations such as high cost, complex procedures, and labor-intensive processes. These factors restrict their usage in remote sensing applications. Therefore, there is a pressing need to develop cost-effective materials that possess high sensitivity, selectivity, good biocompatibility, and exceptional performance to detect Hg2+ ions efficiently. In addition, these materials should be capable of detecting Hg2+ ions at levels as low as parts per billion (ppb) level in the environmental samples [D. T. Quang, J. S. Kim, Fluoro- and Chromogenic Chemodosimeters for Heavy Metal Ion Detection in Solution and Biospecimens, Chem. Rev. 110 (2010) 6280-6301; and E. M. Nolan, S. J. Lippard, Tools and Tactics for the Optical Detection of Mercuric Ion, Chem. Rev. 108 (2008) 3443-3480]. Fluorescence/colorimetric-based optical sensing methods are getting attention for mercury detection. These fluorescent-based materials offer several advantages, such as low limit of detection (LOD), rapid analysis, high sensitivity, and selectivity for environmental pollutant investigations [E. M. Nolan, S. J. Lippard, Tools and Tactics for the Optical Detection of Mercuric Ion, Chem. Rev. 108 (2008) 3443-3480]. A pyrenyl amide-based chemosensor for Hg2+ ions detection in an aqueous environment and found LOD about 1.6 μM has been described [J. S. Kim, M. G. Choi, K. C. Song, K. T. No, S. Ahn, S.-K. Chang, Ratiometric Determination of Hg2+ Ions Based on Simple Molecular Motifs of Pyrene and Dioxaoctanediamide, Org. Lett. 9 (2007) 1129-1132].
Feng et al. [D. Feng, P. Li, X. Tan, Y. Wu, F. Wei, F. Du, C. Ai, Y. Luo, Q. Chen, H. Han, Electrochemiluminescence aptasensor for multiple determination of Hg2+ and Pb2+ ions by using the MIL-53(Al)@CdTe-PEI modified electrode, Anal. Chim. Acta. 1100 (2020) 232-239] fabricated an aptasensor of MIL-53(Al)@CdTe-polyethyleneimine which can be used for electrochemiluminescence (ECL) sensing of Hg2+ and Pb2+ ions at the same single interface. To further improve the LOD, Babamiri et al. [B. Babamiri, A. Salimi, R. Hallaj, Switchable electrochemiluminescence aptasensor coupled with resonance energy transfer for selective attomolar detection of Hg2+ via CdTe@CdS/dendrimer probe and Au nanoparticle quencher, Biosens. Bioelectron. 102 (2018) 328-335] used the ECL resonance energy transfer mechanism for Hg2+ ions sensing. In another study, Kumar et al. [D. Nanda Kumar, N. Chandrasekaran, A. Mukherjee, Horseradish peroxidase-mediated in situ synthesis of silver nanoparticles: application for sensing of mercury, New J. Chem. 42 (2018) 13763-13769] investigated the spectrophotometric detection of Hg2+. The addition of Hg2+ ions reduced the enzyme activity and caused Ag-NPs accumulation, [N. Zhang, J. Xu, C. Xue, Core-shell structured mesoporous silica nanoparticles equipped with pyrene-based chemosensor: Synthesis, characterization, and sensing activity towards Hg(II), J. Lumin. 131 (2011) 2021-2025] prepared Py-SiO2 core-shell NPs by making a receptor of hydrazone moiety for Hg2+ ions.
Based on recent studies, the development of fluorescence sensors for mercury detection at trace levels in an aqueous phase is still considered a challenge. Therefore, there is a need to develop extremely sensitive/selective, easy-to-synthesize, and portable fluorescent sensors to analyze mercury in real sample matrices.
In view of the forgoing, one objective of the present disclosure is to describe a sensor for the detection of mercury ion. A further objective of the present disclosure is to describe a method of making the sensor. A third objective of the present disclosure is to describe a mercury ion detection method.
In an exemplary embodiment, a sensor for the detection of mercury ion is described. The sensor includes a substrate, and a nanocomposite material at least partially covering a surface of the substrate. In some embodiments, the nanocomposite material includes naphthalene-modified silica nanoparticles (NSPs) of formula (I)
In some embodiments, the NSPs contains a naphthalene moiety, a maleic moiety, and an alkylamine functionalized silica nanoparticle. In some embodiments, the naphthalene moiety is covalently linked to the alkylamine functionalized silica nanoparticle via the maleic moiety. In some embodiments, the nanocomposite material has a thermal stability up to a temperature of about 200° C. as determined by thermogravimetric analysis (TGA).
In some embodiments, the substrate includes a silicon portion, and a glass portion.
In some embodiments, the substrate is glass. In some embodiments, the glass is at least one selected from the group consisting of a fluorine-doped tin oxide (FTO) glass, a tin-doped indium oxide (ITO) glass, an aluminum doped zinc oxide (AZO) glass, a niobium doped titanium dioxide (NTO) glass, an indium doped cadmium oxide (ICO) glass, an indium doped zinc oxide (IZO) glass, a fluorine-doped zinc oxide (FZO) glass, a gallium doped zinc oxide (GZO) glass, an antimony doped tin oxide (ATO) glass, a phosphorus-doped tin oxide (PTO) glass, a zinc antimonate glass, a zinc oxide glass, a ruthenium oxide glass, a rhenium oxide glass, a silver oxide glass, and a nickel oxide glass.
In some embodiments, R1, and R2 are each independently selected from the group consisting of hydrogen, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, a nitro group, a sulfonic acid group, a sulfonate group, and a cyano group.
In some embodiments, the naphthalene-modified silica nanoparticles have a formula (II)
In some embodiments, the naphthalene modified silica nanoparticles are uniformly disposed on the surface of the substrate.
In some embodiments, the naphthalene modified silica nanoparticles are in the form of agglomerates having an average particle size of 30 to 90 nanometers (nm).
In some embodiments, the sensor has a zeta potential value of −60 to −20 millivolts (mV).
In some embodiments, the sensor has a maximum fluorescence at the excitation wavelength of 230 to 240 nm.
In some embodiments, the sensor has a capability to detect a ppb concentration level of mercury ions (Hg2+) in the presence of one or more interfering cations selected from the group consisting of La3+, Y2+, Mn2+, Sr3+, Ba2+, Ce3+, Mo3+, Pb2+, Ni2+, Co2+, Ag+, Cd2+, and Cr2+.
In some embodiments, a method of preparing the nanocomposite material is described. The nanocomposite material is prepared by mixing a naphthalene compound, an alkyl amine, and a solvent to form a reaction mixture; portion-wise adding maleic anhydride into the reaction mixture and mixing to form a first intermediate in a first mixture; mixing at least one coupling agent with the first mixture containing the first intermediate to generate a second intermediate in a second mixture; mixing a silane agent and a base with the second mixture containing the second intermediate to generate a crude product in a third mixture; and dialyzing the third mixture containing the crude product, evaporating, and drying to form the nanocomposite material.
In some embodiments, the naphthalene compound has a formula (III)
In some embodiments, the naphthalene compound is 4-amino-3-hydroxy-1-naphthalene sulfonic acid.
In some embodiments, the alkyl amine comprises alkyl groups having 3 to 10 carbon atoms.
In some embodiments, the first intermediate has a formula (IV)
In some embodiments, the second intermediate has a formula (V)
In some embodiments, the method further includes mixing the nanocomposite material and a solvent to form a fourth mixture; and drop casting the fourth mixture onto a surface of the substrate and drying to form the sensor having a layer of the nanocomposite material at least partially covered on the surface of the transparent substrate.
In an exemplary embodiment, a mercury ion detection method is described. The method includes contacting an aqueous composition containing mercury ions with the sensor to adsorb the mercury ions on the naphthalene modified silica nanoparticles and generate a signal corresponding to a fluorescence intensity by the sensor.
In some embodiments, the sensor achieves maximum fluorescence intensity when a mole ratio of naphthalene modified silica nanoparticles present on the sensor to mercury ions present in the aqueous composition is in a range of 1:5 to 1:1.
In some embodiments, the sensor has a detection limit of 1 parts per billion (ppb) by weight for mercury ions, and a linearity range of 0.1 ppb to 10 parts per million (ppm) by weight.
The foregoing general description of the illustrative present disclosure and the following The detailed description thereof are merely exemplary aspects of the teachings of this disclosure and are not restrictive.
A more complete appreciation of this disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In the drawings, reference numerals designate identical or corresponding parts throughout the several views. Further, as used herein, the words “a,” “an,” and the like generally carry a meaning of “one or more,” unless stated otherwise.
Furthermore, the terms “approximately,” “approximate,” “about,” and similar terms generally refer to ranges that include the identified value within a margin of 20%, 10%, or preferably 5%, and any values therebetween.
As used herein, the term “sensor” refers to that which detects the presence, such as measuring the concentration, of an analyte, such as Hg2+ ions, by oxidizing or reducing the analyte at an electrode and detecting, such as measuring, the resulting current. The resulting current need not necessarily be measured as a current but may, for example, be measured as a voltage drop across a resistor.
As used herein, “limit of detection (LOD)” is the smallest concentration of an analyte in a test sample that can be easily distinguished from zero.
As used herein, the term “working electrode” refers to the electrode, the sensor on which the reaction of interest occurs.
As used herein, “linear dynamic range (LDR)” is the range of concentrations where the signals are directly proportional to the analyte concentration in the sample.
As used herein, “selectivity” is the quality of the electrochemical response that can be achieved without interference for any other substance.
As used herein, “sensitivity” is the change in the electrochemical response with regard to a change in the concentration of the analyte.
As used herein, “alkyl” is defined broadly as saturated or unsaturated, branched, or linear non-aromatic hydrocarbons, preferably having 1 to 8 carbon atoms. They may be optionally substituted by non-hydrocarbons.
As used herein, “cycloalkyls” are cyclic alkyls, preferably having 1 to 20 or 5 to 20 carbon atoms, respectively.
As used herein, “alkoxy” refers to an alkyl group, prefearbly having 1 to 8 carbon atoms, which is singularly bonded to oxygen Mercury is one of the most harmful contaminants threatening human lives and the aquatic environment. Naphthalene and its derivatives have fluorescence properties that can be exploited for mercury (Hga+) sensing applications. Aspects of the present disclosure are directed to synthesizing covalently attached naphthalene with silica nanoparticles (NSPs) using a one-pot multiple steps synthesis approach.
A sensor for the detection of mercury ions is described. The sensor includes a substrate onto which is disposed a layer of nanocomposite material covering, at least partially, a surface of the substrate. In some embodiments, the substrate includes a silicon portion and a glass portion.
In some embodiments, the silicon portion and the glass portion in the substrate may be appropriately selected depending on the intended purpose. In some embodiments, the silicon portion in the substrate may include silicon in the form of single-crystal silicon, amorphous silicon, and polysilicon. Further, the glass portion of the substrate is selected from the group consisting of fluorine-doped tin oxide (FTO) glass, a tin-doped indium oxide (ITO) glass, an aluminum-doped zinc oxide (AZO) glass, a niobium-doped titanium dioxide (NTO) glass, an indium-doped cadmium oxide (ICO) glass, an indium-doped zinc oxide (IZO) glass, a fluorine-doped zinc oxide (FZO) glass, a gallium-doped zinc oxide (GZO) glass, an antimony-doped tin oxide (ATO) glass, a phosphorus-doped tin oxide (PTO) glass, a zinc antimonate glass, a zinc oxide glass, a ruthenium oxide glass, a rhenium oxide glass, a silver oxide glass, and a nickel oxide glass. In some preferred embodiments, an area ratio of the silicon portion and the glass portion of the substate may be in a range of 100:1 to 1:100, preferably 1:80 to 80:1, preferably 1:60 to 60:1, preferably 1:40 to 40:1, preferably 1:20 to 20:1, preferably 1:5 to 5:1, or even more preferably about 1:1. Other ranges are also possible.
In some embodiments, the substrate may have a thickness of less than or equal to about 3 mm, for example, preferably ranging from about 0.1 mm to about 2.5 mm, preferably from about 0.3 mm to about 2 mm, preferably from about 0.7 mm to about 1.5 mm, or more preferably from about 1 mm to about 1.2 mm, including all ranges and subranges therebetween. In some preferred embodiments, the substrate may have a thickness of 0.5 mm to 3 mm from the viewpoint of easiness in handling. Other ranges are also possible.
The sensor further includes the nanocomposite material coated at least partially on the surface of the substrate. The deposition of the nanocomposite material on the substrate may be brought about by any of the methods conventionally known in the art, for example, lithographic techniques and drop casting technique. The nanocomposite material includes naphthalene-modified silica particles (NSPs). In an embodiment, the NSPs is a compound of formula (I)
where R1, and R2 are each independently selected from the group consisting of hydrogen, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, a nitro group, a sulfonic acid group, a sulfonate group, and a cyano group. In some embodiments, R1 is a sulfonic acid group. In some embodiments, R2 is a hydroxyl group.
In some embodiments, the NSPs contains a naphthalene moiety, a maleic moiety, and an alkylamine functionalized silica nanoparticle. In some further embodiments, an amine group of the naphthalene moiety is bonded to a first carbonyl group of the maleic moiety. In some further embodiments, an amine group of the alkylamine functionalized silica nanoparticle is bonded to a second carbonyl group of the maleic moiety. In some preferred embodiments, the naphthalene moiety is covalently linked to the alkylamine functionalized silica nanoparticle via the maleic moiety.
In some embodiments, the silica nanoparticles may be of any shape such as spheres, nanotubes, nanowires, tetragons, hexagons, and cylinders, as depicted in
In some embodiments, the naphthalene moiety is present in the naphthalene-modified silica particles (NSPs) at a concentration of 0.5 to 60 wt. % based on a total weight of the NSPs, preferably 5 to 55 wt. %, preferably 15 to 50 wt. %, preferably 20 to 45 wt. %, preferably 25 to 40 wt. %, or even more preferably 30 to 35 wt. % based on the total weight of the NSPs. In some further embodiments, the alkylamine functionalized silica nanoparticle is present in the naphthalene-modified silica particles (NSPs) at a concentration of 10 to 95 wt. % based on a total weight of the NSPs, preferably 20 to 80 wt. %, preferably 30 to 70 wt. %, preferably 40 to 60 wt. %, or even more preferably 50 to 55 wt. % based on the total weight of the NSPs. In some embodiments, the maleic moiety is present in the naphthalene-modified silica particles (NSPs) at a concentration of 0.05 to 20 wt. % based on a total weight of the NSPs, preferably 1 to 15 wt. %, preferably 5 to 10 wt. %, or even more preferably about 10 wt. % based on the total weight of the NSPs. Other ranges are also possible.
In some embodiments, the naphthalene modified silica nanoparticles are in the form of agglomerates, as depicted in
In some embodiments, the naphthalene modified silica nanoparticles are uniformly disposed on the surface of the substrate. It is preferred that the naphthalene modified silica nanoparticles forms a uniform layer that completely covers the surface of the substrate. In some embodiments, at least 50% of the surface of the substrate is covered by the naphthalene modified silica nanoparticles based on a total surface area of the substrate, preferably at least 70%, preferably at least 90%, or even more preferably at least 99%, based on the total surface area of the substrate. In another embodiment, only one side of the substrate is covered with the naphthalene modified silica nanoparticles.
The NSPs were characterized by 1H-NMR, FTIR, TGA, FESEM, XRD, and UV-Vis spectroscopy. The fluorescent properties were analyzed in de-ionized water under normal and UV-light illumination. Finally, the synthesized NSPs were investigated as a chemosensor for Hg2+ ions detection in real seawater samples via PL spectroscopy. The results indicate that the fluorescence properties of NSPs (20 ppm) were quenched upon Hg2+ addition in the range from 0-50 ppm. The experimental studies demonstrated that NSPs acted as a potential host for Hg2+ ions compared to other interfering ions in the seawater sample. The NSPs chemosensor provides a linearity range (0.5 ppb-5.0 ppm) and limit of detection LOD (1 ppb; 5 nM), which is below the values suggested by US EPA drinking water safety regulations.
The crystalline structures of the silica nanoparticles, and the naphthalene modified silica nanoparticles may be characterized by X-ray diffraction (XRD), respectively. In some embodiments, the XRD patterns are collected in a Rigaku diffractometer equipped with a Cu-Kα radiation source (λ=0.15416 nm) for a 20 range extending between 5 and 90°, preferably 15 and 80°, further preferably 30 and 60° at an angular rate of 0.005 to 0.04° s−1, preferably 0.01 to 0.03° s−1, or even preferably 0.02° s−1.
An X-ray diffraction (XRD) pattern of the silica nanoparticles, and the naphthalene modified silica nanoparticles is illustrated in
The photoluminescence (PL) spectra of the naphthalene modified silica nanoparticles may be collected from the spectrofluorometer (FP-8500, JASCO). A sample containing the NSPs in mercury solutions may be exposed to an excitation wavelength of 200 to 800 nm, preferably 300 to 600 nm, or more preferably about 235 nm, and a bandwidth of 1 to 10 nm, preferably about 5 nm.
It is desirable that the sensor of the present disclosure is stable in aqueous environments—for real-time detection of mercury ions in real water samples, for example, seawater, freshwater bodies, lakes, and the like. To achieve this objective, optionally, hydrophilic functionalities, such as SO3H, and hydroxy groups, can be incorporated along with the naphthalene moiety to design a water-stable sensor. In a preferred embodiment, the NSPs have a formula (II)
Referring to
At step 52, the method 50 includes mixing a naphthalene compound, an alkyl amine, and a solvent to form a reaction mixture. The naphthalene compound has a formula (III)
where R1, and R2 are each independently selected from the group consisting of hydrogen, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, a nitro group, a sulfonic acid group, a sulfonate group, and a cyano group. In a preferred embodiment, the naphthalene compound is 4-amino-3-hydroxy-1-naphthalene sulfonic acid. The alkyl amine comprises alkyl groups having 3 to 10 carbon atoms. In an embodiment, the alkyl amine is N,N-diisopropylethylamine. In some embodiments, the molar ratio of the naphthalene compound to the alkyl amine is in a ratio range of 1:1 to 1:5, preferably 1:1 to 1:3, and more preferably about 1:2. Other ranges are also possible.
The solvent may be one or more of acetonitrile, methanol, methyl ethyl ketone (MEK), 1 butanol, t-butanol, tert-butyl methyl ether, triethylamine, toluene, dimethyl formamide (DMF), dimethyl sulfoxide (DMSO). In a preferred embodiment, the solvent is dimethyl formamide (DMF).
At step 54, the method 50 includes portion-wise adding maleic anhydride into the reaction mixture and mixing to form a first intermediate (202) in a first mixture as depicted in
where R1, and R2 are each independently selected from the group consisting of hydrogen, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, a nitro group, a sulfonic acid group, a sulfonate group, and a cyano group.
At step 56, the method 50 includes mixing at least one coupling agent with the first mixture containing the first intermediate (202) to generate a second intermediate (204) in a second mixture, as depicted in
This reaction may be carried out in the presence of one or more coupling agents like (1-cyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylamino-morpholino-carbenium hexafluorophosphate (COMU) N,N′-diisopropylcarbodiimide/hydroxybenzotriazole (DIC/HOBt), N-[(dimethylamino)-1H-1,2,3-triazolo-[4,5-b]pyridin-1-ylmethylene]-N-methylmethanaminium hexafluorophosphate N-oxide (HATU), (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate (PyBOP), n-propylphosphonic anhydride (T3P®), and 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride (EDCI). In a preferred embodiment, the coupling agents are HOBT, and/or EDCI.
The molar ratio of HOBT to EDCI may be in a range of 1:1 to 2:1, preferably about 1.2:1. Similarly, the molar ration of EDCI to APTES is in a range of 1:2 to 2:1, preferably about 1:1. In some embodiments, the molar ratio of HOBT to APTES is in a range of 1:2 to 2:1, preferably about 1.2:1. The reaction is carried out for a period of 18-36 hours, preferably about 20-30 hours, more preferably about 24 hours, to obtain the second intermediate (204). In some embodiments, this reaction may be carried out under anhydrous conditions to prevent hydrolyzation of APTES functional groups, which could cause premature condensation. Other ranges are also possible.
In some embodiments, the second intermediate has a formula (V)
where R1, R2, R3, R4, and R5 are each independently selected from the group consisting of hydrogen, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted alkoxy, a hydroxyl group, a halogen group, a nitro group, a sulfonic acid group, a sulfonate group, and a cyano group.
At step 58, the method 50 includes mixing a silane agent and a base with the second mixture containing the second intermediate to generate a crude product (206) in a third mixture, as depicted in
Suitable examples of silane agents include include, phenyltriethoxysilane (PTES), tetraethoxysilane (TEOS), tetramethoxysilane (TEMOS), n-octyltriethoxysilane, octadecyltriethoxysilane, dimethyldimethoxysilane (DMDMOS), (3-mercaptopropyl) trimethoxysilane, (3-mercaptopropyl) triethoxysilane, (mercapto) triethoxysilane, (3-aminopropyl) triethoxysilane, 3-(2-aminoethylamino) propyltrimethoxysilane, 3-[bis (2-hydroxyethyl) amino] propyltriethoxysilane, hexadecyltrimethoxysilane, phenyltrimethoxysilane, N-[3-(trimethoxysilyl) propyl]-1,2-ethanediamine and acetoxyethyltriethoxysilane, 2-hydroxy-4-(3-triethoxysilylpropoxy) diphenyl ketone, methyltriethoxysilane, vinyltrimethoxysilane; (3-glycidoxypropyl) trimethoxysilane, (benzoyloxypropyl) trimethoxysilane, sodium 3-trihydroxysilylpropylmethylphosphonate, (3-trihydroxysilyl)-1-propanesulphonic acid, and (diethylphosphonatoethyl) triethoxysilane. In a preferred embodiment, the silane agent is TEOS.
The pH of the third mixture was adjusted with a base. The base may be an organic or an inorganic base. In an embodiment, the base is an inorganic base. Suitable examples of inorganic bases include sodium, potassium, or ammonium hydroxide. In a preferred embodiment, the base is sodium hydroxide. The reaction is carried out for a period of 5-15 hours, preferably 7-10 hours, more preferably about 8 hours, to generate the crude product in the third mixture. Other ranges are also possible.
At step 60, the method 50 includes dialyzing the third mixture (252) containing the crude product (206), evaporating, and drying to form the nanocomposite material (258), as depicted in
Optionally, other purification methods such as membrane filtration may be performed instead of dialyses. The dialyses process may be carried out by putting the crude material in a large amount of water. In some embodiments, the dialyses may be carried out with stirring using a stirrer, a magnetic bar, an ultrasonic bath, or a homogenizer, at a temperature of between 0 and 35° C., preferably between 10 to 30° C., more preferably at room temperature, for a period of between 12 hours to and 72 hours, preferably for about 48 hours. Other ranges are also possible. Further to dialyses, the water evaporated by drying to form the nanocomposite material. The drying may be carried out by air-drying or my oven-drying to obtain the NSPs of Formula (I).
The NSPs prepared by the method of present disclosure has a thermal stability up to a temperature of about 200° C. as determined by thermogravimetric analysis (TGA)—in other words, the nanocomposite material is thermally stable, and can withstand the conditions, without loss in chemical/physical properties.
The nanocomposite material thus prepared can be deposited at least partially on the surface of the substrate to form the sensor. The deposition of the nanocomposite material on the substrate is one of the critical factors that affect the performance of the sensor. A drop-casting technique was applied to ensure uniform deposition of the nanocomposite material on the substrate. In this method, a solution containing the nanocomposite material is cast on a substrate, followed by the evaporation of the solvent to obtain the sensor.
To elaborate, the nanocomposite material is mixed in a solvent to form a fourth mixture. Suitable examples of the solvent include, but are not limited to, hexane, chloroform, tetrahydrofuran, dichloromethane, ethanol, and mixtures thereof. The method further includes drop casting the fourth mixture onto a surface of the substrate and drying to form the sensor having a layer of the nanocomposite material at least partially covered on the surface of the transparent substrate. The solvent may be evaporated by drying/heating the substrate at a temperature range of 30-150° C., preferably 50-120° C. Other ranges are also possible. The drying may be performed in a vacuum, microwave, etc. Parameters such as concentration of the nanomaterial composite in the solution, deposition time, thickness of the nanocomposite material on the substrate, temperature, can be varied to obtain the sensor with desired properties. Such variations are obvious to a person skilled in the art. Morphological analysis reveals that the NSPs are uniformly disposed on the surface of the substrate. The NSPs are in the form of agglomerates having an average particle size of 30 to 90 nm. Other ranges are also possible.
The sensor serves as a working electrode in a potentiostat test system. During operation, when the working electrode, reference electrode, and counter electrode are immersed in the liquid to be tested (e.g., seawater), the working electrode communicates with the other electrodes, to generate a test result that is indicative of the concentration of mercury ions in the liquid.
A mercury ion detection method is described. The method includes contacting an aqueous composition containing mercury ions with the sensor to adsorb the mercury ions on the NSPs and generate a signal corresponding to a fluorescence intensity by the sensor. The sensor achieves maximum fluorescence intensity when a mole ratio of the NSPs to the mercury ions present in the aqueous composition is in a range of 1:5 to 1:1, preferably 1:4 to 1:2, or even more preferably about 1:3. Other ranges are also possible. In some embodiments, the signal would increase at least 0.001%, 0.01%, 0.1%, 1%, 10%, 20%, 50%, 70% or more, compared to the signal of a control sample (without Hg2+). For example, an increase in resistance indicates the presence of Hg2+ ions in the sample.
In some embodiments, the sensor prepared by the method of the present disclosure has a detection limit of 1 ppb by weight for mercury ions, and a linearity range of 0.1 ppb to 10 ppm by weight. In some further embodiments, the sensor has a zeta potential value of −60 to −20 mV, preferably −55 to −25 mV, preferably −50 to −30 mV, preferably −45 to −35 mV, or even more preferably about −40 mV. In some preferred embodiments, the sensor has a maximum fluorescence at the excitation wavelength of 230 to 240 nm, or preferably about 235 nm. In some more preferred embodiments, the sensor of the present disclosure has a capability to detect a ppb concentration level of mercury ions (Hg2+) in the presence of one or more interfering cations selected from La3+, Y2+, Mn2+, Sr3+, Ba2+, Ce3+, Mo3+, Pb2+, Ni2+, Co2+, Ag+, Cd2+, and Cr2+ with high selectivity.
The following examples demonstrate the sensor for detecting mercury ions, as described herein. The examples are provided solely for illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the spirit and scope of the present disclosure.
All chemicals were purchased and used without further purification. These chemicals include 4-amino-3-hydroxy-1-naphthalene sulfonic acid (ACS reagent, ≥90%, Sigma Aldrich), sodium hydroxide (≥98%, Flukes, Hampton, USA), 3-aminopropyl) triethoxysilane (APTES, 99%, Sigma-Aldrich), tetraethyl orthosilicate (TEOS, ≥99%, Sigma-Aldrich), hydroxy benzotriazole (HOBT, ≥97%, Sigma-Aldrich), triethylamine (≥99%, Sigma-Aldrich), 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride (EDCI, ≥99%, Sigma-Aldrich), ethyl acetate (≥99.7%, Honeywell, USA), and 1-pyrenecarboxylic acid (97%, Sigma-Aldrich).
1H-NMR spectra were measured on a 400 MHz spectrometer (Bruker AVANCE III) using tetramethylsilane (TMS) as an internal standard and water (D2O) as a deuterated solvent. FTIR spectra were recorded on a PerkinElmer 16F PC spectrophotometer (PerkinElmer Inc. USA) by making pellets of the samples with KBr. The phase of unmodified silica and NSPs were evaluated by an X-ray diffractometer (Rigaku MiniFlexII, Japan) with Cu Kα1 radiation (γ=0.15416 nm). The surface morphology of the samples was analysed via FESEM (Lyra-3, Tescan, Czech Republic), accelerating the voltage up to 30 kV. The samples were dispersed in de-ionized water, deployed on the stubs with double-side Cu-tap, and allowed to dry for 2 h before Au coating. The assessment of organic attachment with silica nanoparticles was also confirmed by thermogravimetric analyses (TGA) using TGA 1 STAReSystem (Mettler Toledo, USA) under Argon atmosphere keeping the flow rate 20 mL min−1 from ambient temperature to 800° C. at a rate of 10° C. min−1. Zetasizer nano (ZEN3600, Malvern, UK) was used to investigate the surface charge and zeta potential of NSPs by dispersing the sample in deionized water. The spectrofluorometer (FP-8500, JASCO) was used to record the PL spectra for developed NSPs and their samples with various mercury solutions at the excitation wavelength (235 nm) and bandwidth (5 nm).
The stock solutions of Hg2+ (100 ppm, 100 mL) were prepared by diluting the standard mercury solution (1000 ppm, Sigma-Aldrich). Then, various dilutions of Hg2+ ions (25 mL) such as (100 ppm, 80 ppm, 60 ppm, 40 ppm, 20 ppm, 10 ppm, 5 ppm, 2 ppm, 1000 ppb, 500 ppb, 200 ppb, 50 ppb, 20 ppb, 10 ppb, 5 ppb, 2 ppb, 1 ppb and 0 ppb) were prepared by applying dilution formula (C1V1═C2V2).
The stock dispersion of NSPs (100 ppm, 100 mL) was prepared by adding 10.0 mg of NSPs in deionized water (100 mL) and dispersed it uniformly by using a probe sonicator (UP400St). Then, the further stock dispersions of NSPs (80 ppm, 60 ppm, 40 ppm, and 20 ppm) were prepared by applying a dilution formula.
Equal volumes of NSPs (40 ppm) and Hg2+ solutions (100 ppm, 80 ppm, 60 ppm, 40 ppm, 20 ppm, 10 ppm, 5 ppm, 2 ppm, 1000 ppb, 500 ppb, 200 ppb, 50 ppb, 20 ppb, 10 ppb, 5 ppb, 2 ppb, 1 ppb and 0 ppb) were mixed in the bottles. The final concentration of NSPs in each bottle was 20 ppm. At the same time, the final concentrations of Hg2+ ions were 50 ppm, 40 ppm, 30 ppm, 20 ppm, 10 ppm, 5 ppm, 2.5 ppm, 1 ppm, 500 ppb, 250 ppb, 100 ppb, 50 ppb, 10 ppb, 5 ppb, 1 ppb and 0 ppb in the final dispersions.
The major cations of seawater such as La3+, Y2+Mn2+, Sr3+, Ba2+, Ce3+, Mo3+, Pb2+, Ni2+, Co2+, Ag+, Cd2+, Cr2+, Na+, K+, Ca2+, and Mg2+ ions were tested for selectivity of mercury sensing. Therefore, the stock solution of each metal cation (100 ppm, 100 mL) was prepared from its standard solution (1000 ppm, Sigma-Aldrich) or by mixing its salts. Then, 40 ppm of the diluted solution was prepared for each metal cation by applying the dilution formula. A similar protocol was adopted for mixing NSPs (40 ppm) dispersion with metal cation solution (40 ppm) to get the final dispersion of 20 ppm each.
FTIR (KBr): v (cm−1)=3467, 2971, 2931, 2880, 1699, 1653, 1384, 1190, 1086, 1049, 767, 657, 457.
1H-NMR (400 MHz, D2O): 6=1.214 (t, 2H), 3.007 (m, 2H), 3.055 (t, 2H), 6.787-6.928 (2×d, 1H), 7.455-7.539 (2×d, 1H), 7.676-7.774 (2×d, 1H), 8.427-8.465 (d, 1H).
The spectrofluorometer was employed to record the PL spectra of NSPs at 235 nm. The developed NSPs were ultrasonicated for 60 min in DI water to get a well-dispersed suspension. All the measurements for Hg2+ solutions (0.5 ppb-50 ppm) and other cationic solutions (0.05 mM) were performed under ambient conditions. The sequential increment in the concentrations of Hg2+ ions from 0.5 ppb to 50 ppm was used to evaluate the sensing properties of NSPs (20 ppm). The selectivity of NSPs for Hg2+ was also assessed in the presence of pervasive cations (i.e., La3+, Y2+, Mn2+, Sr3+, Ba2+, Ce3+, Mo3+, Pb2+, Ni2+, Co2+, Ag+, Cd2+, Cr2+, Ca2+, Mg2+, K+, Na+, and seawater samples). Fluorescence spectra were taken 20 minutes after dissolving the metal cations in DI water and mixing them with the sensor. The seawater salinity was calculated and found to be about 36.03 g/L.
The synthesis of covalently attached naphthalene-based silica NPs was accomplished using the one-pot multistep synthesis approach. In this method, initially, a ring-opening reaction was carried out between maleic anhydride and 4-amino-3-hydroxy-1-naphthalene sulfonic acid in the presence of Hunig base [O. Abdulaziz Alghamdi, M. Mansha, A. N. Kalanthoden, M. S. Kamal, M. Khan, Fracturing fluid applications of carboxylate-terminated low molecular weight PEI and CTAB formulations, Colloid Interface Sci. Commun. 49 (2022) 100643; and M. Mansha, A. Madhan Kumar, A. Y. Adesina, I. B. Obot, M. Khan, A novel trans-esterified water soluble hyperbranched polymer for surface protection of X60 steel: Experimental and theoretical approach, J. Mol. Liq. 349 (2022) 118091, each incorporated herein by reference in their entirety]. The formed intermediate I was allowed to undergo an amide coupling reaction with APTES in the presence of EDCI and HOBt coupling agents [M. Mansha, U. U. Kumari, Z. Cournia, N. Ullah, Pyrazole-based potent inhibitors of GGT1: Synthesis, biological evaluation, and molecular docking studies, Eur. J. Med. Chem. 124 (2016) 666-676; and M. Mansha, N. Ullah, K. Alhooshani, Synthesis of structural analogues of GGT1-DU40, a potent GGTase-1 inhibitor, Zeitschrift Für Naturforsch. B. 71 (2016) 333-344, each incorporated herein by reference in their entirety] to make intermediate II. The hydrolysis reaction followed by condensation was carried out by adding TEOS under basic conditions maintaining pH ≥9 (Stobers synthesis program) [S. A. Khan, M. H. Al-Jabari, M. Mansha, S. Ali, Z. H. Yamani, Hydrophobic, partially hydrophobic, and hydrophilic ZnO@SiO2 nanoparticles as fluorescent partitioning tracers for oil sensing applications, J. Mol. Liq. 360 (2022) 119505, incorporated herein by reference in its entirety]. The obtained product has high dispersibility or affinity in the water phase and shows no significant partitioning behavior in any organic solvent. The remaining product in the water phase was purified using a dialysis membrane. All the unreacted materials and reagents soluble in water were removed during the dialysis.
The chemical structure of NSPs was investigated by 1H-NMR and FTIR spectroscopy. The 1H-NMR spectrum of NSPs showed that methylene protons of (—NH—CH2—CH2—CH2—Si(O3)—), (—NH—CH2—CH2—CH2—Si(O3)—) and (—NH—CH2—CH2—CH2—Si(O3)—) detected at 1.197 ppm, 2.980 ppm, and 3.006 ppm, respectively, in deuterated water solvent [F. Kunc, V. Balhara, A. Brinkmann, Y. Sun, D. M. Leek, L. J. Johnston, Quantification and Stability Determination of Surface Amine Groups on Silica Nanoparticles Using Solution NMR, Anal. Chem. 90 (2018) 13322-133309, incorporated herein by reference in its entirety]. The alkene component (—HC═CH—) of the molecule appeared between 6.787-6.928 ppm as two doublets. The aromatic protons of naphthalene appeared between 7.455-8.465 ppm, where the proton attached to 2C adjacent to hydroxyl and sulfonic acid functional groups, and the proton as a substituent at 6C appeared in the region of 7.455-7.539 ppm, while the protons substituents at 7C and 8C showed between 7.676-7.774 ppm. The proton of the 9C position appeared between 8.427-8.465 ppm (
The nature of functional groups for intermediate I, II, and NSPs was ascertained by FTIR spectroscopy (
The thermal stability of naphthalene-based (organic moiety) NSPs was investigated by heating the material from room temperature to 800° C. (
The approximate surface charge and zeta potential value of the synthesized NSPs were determined in deionized water by the dynamic light scattering (DLS) technique. The zeta potential value of NSPs predicts them as negatively charged species having a value of −42 mV (
The crystal structure and purity of unmodified silica nanoparticles and the NSPs were investigated by X-ray diffraction (XRD) analysis. The amorphous nature of silica NPs was confirmed by observing a broad diffraction peak in the XRD pattern that appeared at 20 position of 23°, as illustrated in
The surface morphology and particle size of as-synthesized particles were observed via field emission scanning electron microscopy (FESEM).
The measurement of the UV-Vis spectrum of NSPs showed three different absorption peaks appearing at 235 nm, 290 nm, and 336 nm, respectively (
After the UV-visible spectrum analysis, the maximum intensity of fluorescence emission was measured via photoluminescence studies by exciting the molecule at different wavelengths, such as 200 nm, 240 nm, 280 nm, and 320 nm. The results showed that the excitation wavelength of 240 nm exhibited maximum fluorescence intensity (about 6200 a.u.) as compared to other low-energy wavelengths (
The luminescent characteristics of NSPs solution in de-ionized water with and without mercury ions were also examined under normal light and UV-light illumination (
The photoluminescence (PL) spectra of NSPs were recorded by measuring the fluorescence emission intensity versus wavelength in the range of 320-650 nm. By considering the UV-Vis (
Where KSV, Q, F, and F° are Stern-Volmer constant, quencher concentration, and fluorescence intensity of the chemosensor with and without Hg2+ ions, respectively [J. Keizer, Nonlinear fluorescence quenching and the origin of positive curvature in Stern-Volmer plots, J. Am. Chem. Soc. 105 (1983) 1494-1498, incorporated herein by reference in its entirety]. The static quenching was again confirmed from the straight line observed in the Stern-Volmer plot between F°/F and [Q], as demonstrated in
The assessment for the selectivity of NSPs for Hg2+ ions (10 ppm, 0.05 mM) in the presence of various cations such as La3+, Y2+Mn2+, Sr3+, Ba2+, Ce3+, Mo3+, Pb2+, Ni2+, Co2+, Ag+, Cd2+, and Cr2+ was determined (
The NSPs chemosensor was also used to test the real seawater sample in the presence of Hg2+ ions (10 ppm, 0.05 mM), as shown in (
The results exhibited that the developed NSPs chemosensor has comparable detection capabilities and, in some cases, even better than reported techniques for the Hg2+ ions sensing in the aquatic environment, as shown in Table 1. Generally, colorimetric chemosensors are considered less sensitive than electrochemical and SERS-based sensors. However, a minute change in the sensing environment may cause a dramatic change in the selectivity of an electrochemical sensor. Likewise, Hg2+ ions can be detected with five ppb LOD by using a SERS-based probe [T. Senapati, D. Senapati, A. K. Singh, Z. Fan, R. Kanchanapally, P. C. Ray, Highly selective SERS probe for Hg(ii) detection using tryptophan-protected popcorn shaped gold nanoparticles, Chem. Commun. 47 (2011) 10326, incorporated herein by reference in its entirety]. Moreover, a dithizone-based sensor can detect 10 ppb by colorimetric technique [R. Sedghi, B. Heidari, H. Javadi, N. Sayyari, Design and synthesis of colorimetric sensor based on dithizone@TiO2/poly (tert-butyl acrylate-acrylic acid) nanocomposite for fast visual detection of mercury, lead and cadmium ions in aqueous media, Environ. Nanotechnology, Monit. Manag. 18 (2022) 100670, incorporated herein by reference in its entirety]. The comparison indicates that the designed NSPs exhibit exceptional chemosensors for Hg2+ ions detection at a very low level (LOD: 1 ppb) in real seawater. Furthermore, the one-step synthesis and trace-level detection of Hg2+ ions give advantages to other sensors reported in the literature (Table 1).
The mechanism for Hg2+ ions quenching by NSPs chemosensor can be explained based on complex formation of Hg with chemosensor at N and O active sites in the structure by making a stable Penta-ring. Furthermore, the estimation of binding stoichiometry between NSPs and Hg2+ ions was conducted by Job's plot analysis (
Naphthalene-based silica nanoparticles were synthesized using a one-pot multiple steps synthesis approach. The chemical structure of NSPs was confirmed by 1H-NMR and FTIR spectroscopy. The covalent attachment of naphthalene-based organic species with silica nanoparticles was verified by thermal gravimetric analysis by observing the weight loss between 125-400° C. A broad diffraction peak appeared at 20 position (about 23°), confirming the formation of amorphous silica NPs. FESEM images showed the average particle size of unmodified silica and NSPs around 40 and 60 nm, respectively. At the same time, the zeta potential value of NSPs (−42 mV) predicts that the NSPs are highly stable in the aqueous phase due to the presence of sulfonate (—SO3H), hydroxyl (—OH), and amide (—NHCO—) functionalities at the surface of silica particles. The UV-Vis absorption band was observed at 235 nm due to π→π* electronic transitions of the naphthalene ring and showed dark blue color under UV-light illumination. The PL spectral intensity of NSPs was suppressed upon Hg2+ addition, attributed to the formation of a stable Hg-based complex with NSPs. The static quenching phenomenon was confirmed from the Stern-Volmer plot, and the Ksv value of NSPs in the presence of Hg2+ ions was 0.409×106 M−1. The chemical structure and PL results indicate that NSPs behave as an internal charge transfer (ICT) chemosensor due to electron-donating and accepting groups within conjugated π systems without a spacer. The developed NSPs chemosensor can reliably recognize Hg2+ ions (LOD: 1 ppb) with a linearity range (0.5 ppb-5.0 ppm) in a real seawater sample. The developed fluorescent chemosensor (NSPs) have great potential as highly sensitive, selective, and portable opto-chemical mercury sensors for seawater applications.
Numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
